Tubular steam boiler



May 19, 1959 H. voRKAUF TUBULAR STEAM BOILER Filed Aug. 2o,l 1954 l M ||i H. lo

United States Patent O TUBULAR STEAM BOILER Heinrich Vorkauf, Berlin-Schmargendorf, Germany Application August 20, 1954, Serial No. 451,201

Claims. (Cl. 122-235) This invention relates to a steam boiler of the type including a steam and water drum in association with a tubular framework connected in the water circulatory system of the boiler. t

The present application is a continuation-in-part of my copending patent application Serial Number 145,948, led February 24, 1950, now abandoned.

In the present invention and also in the structure shown in the above mentioned application, the framework of the boiler comprises four rectangularly spaced, vertical, corner tubes which are unheated. The framework further comprises upper and lower tubes, longitudinally and transversely of the boiler structure. At least two of the corner tubes are connected to the upper and lower tubes. A steam and water boiler drum communicating with the upper and lower tubes may be so arranged that it is also a part of the boiler framework. Convective evaporating tubes are connected between the upper and lower framework tubes which, as well as the convective evaporating tubes are exposed to the heat from the boiler furnace. Owing to this structure, the upper tubes serve as collectors, the lower tubes as distributors, and at least the pair of the mentioned corner tubes may serve as return pipes.

According to an important feature ofthe present invention, the longitudinal collector tubes are connected to the mentioned pair of corner tubes approximately at the height of the mean water level of the boiler drum and preferably at a level at least as high as that water level.

The collector tubes may be horizontal between their connections with the corner tubes and the drum or may even slightly rise towards the drum. In other words, the connectionofthe collector tubes with the drum should be on a level at least as high as the level of their connection l `This part of the waterwill thus bypass the boiler drum.

flfhe remaining part of the circulating water, that is, that partof the Water not yet separated from the steam, and all of the steam, both separated and unseparated from the Patented May 19, 1`959 rected current of returnwater which bypasses the drum. Owing to this ow of return water, the time for starting the boiler is considerably reduced. This characteristic obtains since heated water will ow immediately through the return or bypass corner tubes to the heating surfaces, whereas flow of heated water from the drum is not possible until its entire water content is raised to a certain temperature.

A further advantage derives from the arrangement, in that during normal operation of the boiler the partial separation of the steam and Water before passage of the mixture to the drum, and the bypassing of the drum by the water demixed from steam during said partial separation, relieves the drum considerably. The cross-sec tional areas of the tubular connections to the drum ma thus be materially reduced.

The feature wherein at least two of the vertical, un heated corner tubes are connected to the collector tubes approximately at the height of the mean water level of the drum, has been found to be of great. importance in producing the above described action. Tests have shown that the drum-bypassing return water flow will be stemmed Or even turned in an opposite direction if the connection of the tubes destined to conduct the return flow, with the collector tubes receiving the steam-water mixture from the evaporation tubes is located below the water level of the drum. This, it has been found, is true because when the speciied connection is lower than the mean water level, the lifting power of the lighter steam-water mixture creates an upwardly directed suction within the tube which is intended to function as the drum-bypassing down pipe or return tube. Such a lifting effect cannot occur if the connection of the return tubes with the collector tubes is made at the height of the mean water level of the drum since, under these circumstances, the static pressure of the water column in said return tubes must and will be exactly as great as the static pressure prevailing in `the down pipes connected directly between the water space of the drum and the distributor tubes at the lower end of the boiler, to which tubes all water circulated in the system flows.

It is another object of the invention to provide a particular formation, and relative arrangement of corner tubes, distributor tubes and collector tubes that will constitute an improved framing structure for the boiler. It is further proposed, in at least one form ofthe invention, to incorporate the boiler drum `as part of said framing structure. v

Further objects and details of the invention will be ap-` parent from the description given hereinafter and the accompanying drawing illustrating several embodiments thereof by way of example.

water will, `in the meantime, tlow within the collector tubes tothe boiler drum, where said remaining part of the water separates from the steam. The water separated within the drum from the steam then ows through down pipes, which in at least one form of the invention may comprise the remaining two `corner tubes, tothe distributor tubes for recirculation.

The conection of the collector tubes with the first mentioned pair of corner tubes substantially at the height of the mean water level in the drum insures `in these cprner tubes, under all boiler loads, `a downwardly di- In the drawings: Fig. l is a vertical sectional view through a tubular steam boiler of the single draft type formed in accordance .7, with the invention,

Fig. 2 is a horizontal sectional view on line 2-2 of Fig. 1, and

Fig. 3 is a View similar to Fig. l showing the invention incorporated in a multiple draft steam generator of the type having a horizontal drum and a traveling grate.

In the embodiment of the invention shown in Figs. l and 2, the boiler has been designated generally by the reference numeral 10. At its lower end, the boiler is provided with straight, parallel, horizontally disposed,

y longitudinal lower tubes 11. Extending normally to the tubes 11` are a horizontal rearlower transverse tube 12, and a front lower transverse tube 13. As shown, the tube 12 may be at a level slightly above the common horizontal plane of longitudinal tubes 11, while tube 13 maybe `at a level slightly above that of the tube 12.y

The several lower tubes serve as distributor tubes, and are exposed during operation of the boiler to the heat from the furnace the grate of which is indicated at 40. At the upper endl of the system, I provide an upper transverse tube 14 and, normal to the tube 14, a pair of parallel, upper longitudinal tubes 15. The tube 14 and tubes 15 of the illustrated embodiment are all disposed in a common horizontal plane.

The tubes 14, 15 all serve simultaneously as collector tubes, to which flows a steam-water mixture generated in banks of vertically extending convective evaporation tubes 17. These are heated during operation of the boiler, and as shown in Fig. 1, one bank of tubes 17 is connected between the upper and lower transverse tubes 14, 13, respectively, and extends within a vertical plane including the tube 14 and tube 13. At the sides of the structure, banks of tubes 17 are connected between the upper and lower horizontal tubes 15, 11, the tubes 17 at each side of the structure extending within a common vertical plane including the tubes 15, 11 to which they are connected at their opposite ends. At the back of the structure, tubes 17 are connected at their lower ends to the rear lower tube 12, and extend upwardly into communication with inclined tubes 30. These are arranged longitudinally of the boiler between the opposite sides thereof, in an array of parallel rows of straight tubes disposed in inclined positions, and openingy at their opposite ends into the tubes 17' at the front and back of the boiler.

At the four corners of the boiler structure I provide vertical, unheated corner tubes 16. These are connected at their upper ends to the end portions of the several collector tubes 14, 15, the connection of these tubes being located substantially at the height of the mean water level t)` in a boiler drum 18. At their lower ends, the corner tubes 16 are connected in communication with the transverse and longitudinal distributor tubes 11, 12, 13.

The boiler drum 1S is disposed vertically, in the form ofy Fig. l, in front of the front bank of tubes 17. The front ends of the longitudinal collector tubes 15 are provided with forwardly convergent extensions 31, which at their convergent ends extend into communication with the boiler drum. In Fig. l the extensions 31 are in the common horizontal plane of the several collector tubes. However, this is not necessarily so, it being merely required that no point of the longitudinal collector tubes including the extensions 31 is located below the level of the connection of the tubes 15 with the corner tubes 16. In other Words, the longitudinal collector tubes and their associated extensions 31, while being essentially horizontal, may rise slightly from their rear ends in the direction of their front ends, if desired.

The collector tubes extend into communication with the boiler drum close to the mean water level 50 thereof. The lower end of the water space 51 of the drum is connected to the distributor tubes 11. For this purpose, a short tubular piece 19' leads downward from the drum and branches into twoy downwardly divergent down pipes 19 which, at their lower divergent ends, extend into communication with the respective longitudinal distributor tubes 11.

In operation, on the heating of Water in the boiler, a steam-water mixture is generated in the convective tubes 17, and this mixture ascends to the collector tubes 14, 15. Within the collector tubes, a partial separation of steam and water occurs at the conventional speed prevailing in natural circulation. Due to the fact that the return pipes 16 communicate with, that is, are connected to the collector tubes 15 substantially at the mean water level of the boiler drum, that part of the water separated from the steam during this initial separation flows into the corner tubes 16 and back to the heated tube system through the tubes 16 and distributor tubes 11, 12, 13. This part of the water in the system thus bypasses the drum.

The steam separated from the returning or drum-bypassing water during the mentioned initial separation ass-'m95 a travels on. to the boiler drum together with the still remaining steam-Water mixture. Here nal separation occurs. The water in the drum resulting from the final separation flows from the lower end of the water space of the drum through the down pipes 19 into the distributors for recirculation, together with the water that ows back to the distributors through the down pipes 16 and together, further, with such additional water as may be necessary to be supplied to substitute for water evaporated during the operation of the boiler.

Thev water columns in the several corner tubes 16 are approximately as high las the water column within the water space of the drum and the down pipe 19, i.e. the water column between the water level Sil in the drum and the distributors 11. Therefore, the water flows from the water space of the drum, and from the corner tubes 16 to the tubular system with approximately equal static pressure. It will be clear that a portion of the water :separated from the mixture within the collector tubes 1S may also return to the distributors 11 through the front corner tubes 16, as the water columns of these tubes are of the satne height as those in the tubes 15 if the collector tubes are horizontal-ly disposed.

Referring to Fig. 2, since the tubes 16 are to be unheated, ribs or shields 21 are provided which extend diagonally of each corner of the rectangular framework, so as to be interposed between the tubes 16 and the heat applied to the tubular system. Each of these ribs is connected fixedly along its vertically extending side edges to those tubes 17 that are immediately adjacent the associated corner tube 16 at opposite sidesv of said corner tube. Other ribs are secured to and between each pair of adjacent tubes 17, throughout the periphery of the structure to prevent the insulation 41, located exteriorly of the system from falling through the spaces 'between the tubes 17 In Fig. 3, the boiler has been generally designated at 32. In this .form of the invention, the boiler drum 22 is horizontally, rather than vertically disposed, and extends transversely of the upper end of the boiler, at the front ofl the tubular framework. In this arrangement, the rectangularly spaced arrangement of corner tubes is again utilized, so that there are vertical front corner tubes 23 and vertical rear corner tubes 24, at the several corners of the structure. A lower front distributor tube 25 extends horizontally of the frame, transversely thereof and is connected lat its opposite ends to the lower end portions of the front corner tubes 23. Longitudinal lower tubes 26 are connected to the lower` ends of the corner tubes 23, 24 at opposite sides of the framework, and also are horizontally disposed. A rear, transverse lower tube 27 is connected between the lower end portions of the corner tubes 24.

In the Figure 3 form of the invention, the drum itself serves as part ofthe tubular framework, and is connected directly at the bottom of its water space 61 to the upper ends of' the front corner tubes 23. The drum is also connected to the front ends of upper longitudinal framework tubes 29, which serve as collectors and are horizontally disposed along opposite sides of the upper end of the boiler. The tubes 29 open at their front ends into the drum 22 and are connected at their rear ends to the upper ends of the rear corner tubes 24. An upper hon'- zontally disposed transverse tube 28 is connected between` the upper ends of the corner tubes 24, immediately below the connections of the corner tubes 24 to the collector tubes 29. It will be noted, and is an important part of theV invention, that the connection between the corner tubes 24 and the collector tubes 29 is approximately at the mean water level 60 of the drum 22.

Extending vertically between and connected in communication with the collector tubes 29 and distributor tubes 26 are the convective evaporation tubes 33.

The functional characteristics' of the Fig. 3 form of the invention are the same las in the rst form. Thus',

a steam-watermixturegenerated inthejeuaporation tubes 33 ascends to the collector tubes 29. Here a great part of the separation of the mixture occurs. Allthe steam and a part of the water flows to the drum Z2, While the remaining part of the water, deriving from the separation occurring within the tubes 29, flows directly Iback to the heated tubular system `through the rear corner tubes 24, thus bypassing the drum 22. Hence, the corner tubes 24 serve as return pipes, whereas the front corner tubes 23, connected to the bottom of the Water space of the drum 22, serve as down pipes yanalogous to the` down pipes 19 in the first form. Again, as in the first form of the nvention, the static pressure of the water column within the corner tubes or return pipes 24` is thesame as that defined betweenthe water-level 60 of the drum and the lower ends of the down pipes 23. This is due to the fact that the return pipes 24 are connected to the tubes 29 approximately at the height of the mean Water level within the drums.

It will be understood that While in the illustrated example a steam generator having a traveling grate 61 furnace has been shown, the invention will of course be fully applicableto anyother kind of furnace.

In both forms of the invention there is also the common important characteristic wherein the tubular system illustrated constitutes the framework of the boiler, about which the boiler is constructed, the corner tubes in both forms serving as the vertical corner posts of the rectangular framework defined by the system. Important advantages derive from `the particular construction shown, since the corner tubes form la water-cooled boiler framing in connection with transverse and longitudinal framing elements. The corner tubes and the longitudinal and transverse elements constitute a framing that is the sole support of the boiler heating surfaces and of the drum. Since the corner tubes are. unheated, heat stresses are avoided that would otherwise be imposed upon the framing. In a normal boiler framing consisting of profiled iron, stresses occur when the framing is subjected to a `considerable range of temperatures during the use of the boiler. These stresses are avoided in a framing such as that shown,l through which the water of the boiler flows, since in such a case the temperature tends not to fluctuate through as wide a range as it would in a conventional boiler framing. l

Thus the invention provides a tubular steam boiler with a twofold natural water circulation which takes place, without artificial means, through parts of the tubular framework of the boiler. The desired elect will be obtained by locating the connection between the collectors and the return pipes at a level at least as high as the water level in the drum. If this connection is raised above the water level the separation of the steam-water mixture may be somewhat improved. However, this advantage is likely to be balanced by a disadvantage consisting in a decrease of the circulation caused by the fact that the boiler water must be raised in the risers above the water level in the drum. Hence, it depends on the magnitude of the circulation how much higher the mentioned connection may be located than the water level. In most cases, therefore, it will be preferred to connect the collectors and the return or down pipes substantially at a level as high as the mean Water level in the drum.

It will be apparent to those skilled in the art that many alterations and modifications of the structure illustrated and hereinbefore described can be made without departure from the essence and spirit of the invention which shall not be limited but by the scope of the appended claims.

I claim:

1. In a tubular steam boiler, a boiler drum with a mean Water level therein, at least one pair of generally vertical return pipes located in two adjacent corners, respectively, of two opposite sides of said boiler, a pair of parallel, generally horizontal collector tubes substantially along` said boiler sides, respectively, and connected with one of their ends to the drum and with their other ends to the upper ends of the respective return pipes, generally horizontal, parallel distributor tubes substantially along said boiler sides, respectively, and connected to the lower ends of the respective return pipes, two sets of substantially vertical evaporation tubes, said sets being connected between the distributor and collector tubes on said op.- posite boiler sides, respectively, and down pipes connected between the water space of the drum and the distributor tubes, the connections of the -return pipes to the collector tubes being at a level approximately as high as the mean water `level of the drum, and no part of'said collector `tubes being lower than their connection to said return pipes.

2. In a tubular steam boiler with natural circulation, a boiler drum having a steam space and a water space, said drum being located at the adjacent ends of two opf posite sides of the boiler, a pair of unheated down pipes in the corners, respectively, at the opposite ends of said two opposite sides of the boiler, a pair of substantially horizontal collector tubes substantially along said opposite boiler sides, respectively, a pair of distributor tubes substantially along said opposite boiler sides, respectively, two sets of substantially vertical evaporation tubes said sets connecting said distributors to said collectors of said opposite sides, respectively, said distributors being connected to said water space of said drum and to the lower end portions of said down pipes, respectively, each collector tube being connected with one of its ends to the upperportion of one of said down pipes and with its other `ends to said drum, the points of connection of said colector tubes with said down pipes being on a level approximately as high as the mean waterl level in said drum, and the points of connection of said collector tubes and said drum being on a level at least as high as the connection of said collector tubes to said down pipes.

3. Inra tubular steam boiler with natural water circulation the combination of a boiler drum having a steam space and a water space and being located on opposite sides at the one end of the boiler, a tubular boiler frame including a pair of vertical pipes constituting down pipes in the corners, respectively, at the opposite end of the boiler, a pair of lower longitudinal tubes constituting distributors, and a pair of upper longitudinal tubes constituting collectors, one of said collectors and one of said distributors being located along each of said opposite sides, said collectors and said distributors being connected with one of their ends to said corner tubes, and substantially vertical evaporation tubes connecting said distributors to said collectors of the opposite sides, respectively, the other ends of said distributors being connected to the water space of said drum, the points of connection of said collector tubes with said corner tubes being approximately at a level as high as the mean water level in said drum, and the other ends of said collector tubes being connected to said drum at a level at least as high as said points of connection, whereby one natural water circulation is set up through said drum and its connecu tion to said distributors, and another natural circulation is set up through said down pipes.

4. A steam boiler as in claim 3, said framework further comprising a second pair of corner tubes located between both said boiler ends, each corner tube of said second pair being connected to one of said collectors and one of said distributors, said drum extending in a vertical direction and being connected with its lower end to both said longitudinal distributor tubes.

5. A steam boiler as in claim 3 wherein said drum extends transversely of said collector tubes, thereby constituting a transverse connection of said framework, said framework further comprising a second pair of corner tubes extending as the connection between the water space of the drum and the distributor tubes.

l6. In a tubular steam boiler, two of approximately vertical, unheated rst tubes located in adjacent corners, respectively, of the boiler, a pair of longitudinal collector tubes on opposite sides, respectively, of said boiler and connected to the upper ends of said lirst tubes, a boiler drum having a water space, the collector tubes extending between the drum and said first tubes, a plurality of approximately horizontal distributor tubes connected between the lower ends of said first tubes, two sets of substantially vertical evaporation tubes connected between the distributor and collector tubes of said opposite sides, respectively, and down pipes connected between the water space of the drum and the distributor tubes, the connection of the collector tubes to the iirst tubes being at a level substantially as high as the mean water level of the drum and the connection between the collector tubes and the drum being at a level at least as high as the connection between the collector tubes and said first tubes, whereby a steam-water mixture generated in the evaporation tubes will be partially separated Within the collector tubes, at least part of the water separated from `steam in the collector tubes flowing back to the distributor tubes through the first tubes, thereby to bypass the drum, and the remaining Water and all the steam owing to the drum for final separation and for return of said remaining water through the down pipes to the distributor tubes.

7. A tubular steam boiler as in claim 6, wherein there are four of said tirst tubes rectangularly spaced apart and located at the several corners of the boiler, said collector tubes extending between the first tubes at the respective sides of the boiler.

8. In a tubular `steam boiler with natural circulation the combination of four non-heated down pipes at the corners of a quadrangular structure, a pair of distributor tubes on opposite sides of said structure, each distributor tube being connected to the lower ends of the adjacent down pipes, a horizontally located boiler drum having a steam and a water space, said drum being carried by and connected with its water space to the upper ends of the pair of down pipes at the corners of a third side of said structure, a pair of substantially horizontal collector pipes on said opposite sides of said structure, respectively, said collector pipes being connected with one of their ends to the upper ends of the down pipes, respectively, at the corners of the fourth side of said structure and substantially at the level of the mean water level in said drum, the other ends of said collector pipes being connected to said drum at a level at least as high as that of their iirst mentioned ends, and a plurality of evaporation tubes connecting each distributor tube to the collector tube on the same side of said structure, whereby two paths for natural circulation are provided, both said paths including at least portions of said distributor tubes, evaporation tubes, and collector tubes, and one of said paths further including said drum and the down pipes carrying said drum, and the other path including the down pipes at the corners of said fourth side of said structure.

9. A steam boiler as in claim 8, further comprising a furnace within said structure, all said distributors, evaporation tubes and collectors being exposed to the heat of said furnace.

10. In a boiler the combination of at least one pair of horizontal longitudinal vdistributors on opposite sides of the boiler, respectively, vertical non-heated down pipes at the ends of said distributors, at least one transverse tube connecting said distributors and vertical pipes, a pair of horizontal longitudinal collectors on said opposite sides, respectively, a plurality of heated vertical risers, said collectors being connected to said distributors, respectively, by said risers, a main transverse collector directly connected to said longitudinal collectors at such a distance from the one end of said longitudinal collectors that a current takes place through a substantial length of said longitudinal collectors to said main transverse collector, a pair of said down-pipes at said one end of said longitudinal collectors being connected to and communicating with the latter and said distributors so as to serve as return pipes.

References Cited in the tile of this patent UNITED STATES PATENTS 439,684 Pratt Nov. 4, 1890 1,712,806 Baker May 14, 1929 1,903,515 Monroe Apr. 11, 1933 FOREIGN PATENTS 371,290 Italy May 17, 1939 

